Collection of thousands, and in some cases millions, of chemical compounds are referred to in the pharmaceutical industry as chemical libraries. Methods have been developed for screening the compounds from a chemical library in an effort to identify, as an example, novel ligands or other the like that can be the basis for a new and effective pharmaceutical drug or the like.
Recently developed synthesis techniques are capable of generating large chemical libraries in a relatively short period of time as compared to previous synthesis techniques. As an example, automated synthesis techniques for sample generation allows for the generation of up to 4,000 or more compounds per week. These samples can include impurities in addition to the desired compound. When samples having these impurities are screened against selected targets, such as a novel ligand or a biological receptor, the impurities can produce erroneous screening results. As a result, samples that receive a positive result from initial screening must be further analyzed and screened to verify the accuracy of the initial screening result. This verification process requires that additional samples be available. The verification process also increases the cost and time required to accurately verify that the targeted compound has been located. Samples can be purified in an effort to achieve an 85% purity or better. Screening of the purified samples provides more accurate and meaningful biological results. Conventional purification techniques, however, are slow and expensive. Conventional purification techniques using high-pressure liquid chromatography (HPLC) take approximately 30 minutes to purify each sample. Therefore, purification of the 4,000 samples generated in one week would take at least 2,000 hours (i.e., 83.3 days or 2.77 months).
There are many different configurations of purification instruments. They typically share commonality in the concept wherein the samples are delivered to a chromatography instrument. The chromatography instrument separates the compounds in time and a fraction collector collects the target compound. A substantial improvement in high throughput purification of samples was developed by Ontogen Corporation of Carlsbad, Calif., U.S.A., which developed a multiple-channel, high throughput supercritical fluid chromatographic purification system. The system is described in U.S. Pat. No. 6,309,541, issued Oct. 30, 2001, which is incorporated herein in its entirety by reference thereto.
The Ontogen purification system simultaneously handles multiple sample flows through the system's multiple purification channels. Each channel uses a stand-alone detector capable of identifying in real time a peak within the sample flow if the peak has selected characteristics. The conventional detectors are UV detectors that identify when a sample with certain absorption characteristics (e.g., a set level of absorption units at selected wavelengths) flowing through the detector. An UV absorption profile for a compound can, however, vary over a range of wavelengths, so some conventional detectors may not detect desired samples with peaks at different absorption wavelengths within the spectrum.